In a conventional radio communication system with a plurality of radio base stations, sizes of cells, which are communication regions provided by respective radio base stations, are preliminarily determined at its design stage. Parameters for determining a coverage of the cell include radio parameters such as a transmission power of a radio base station, a tilt angle of an antenna in the radio base station, and a direction and a shape of a beam that is output from the antenna.
For example, in the case where a coverage of a cell is changed during operation of the radio communication system, a provided service is stopped and then the radio parameters are manually adjusted, or the radio base station itself is manually exchanged. In the case where the setting of the radio parameters is adjusted, it is preferred that the adjustment be performed considering an influence on communications of another nearby radio base station. Additionally, these works are preferred to be carried out every time an installation position of another nearby radio base station or a volume of communication is changed. This consequently increases time and cost for maintenance. In view of this, a radio base station autonomously adjusts its coverage of cell with a recent technique.                Patent Document 1: Japanese Patent No. 3703764        